Introduction: This article gives the process of forming a multimeter networking conversion module in ESP32. After the transformation, the universal networking data can be accessed through UDP.

关键词: Multimeter , ESP32

01 Multimeter networking

1. Background introduction

Because the computer suddenly could not detect the USB serial port line , I made a module to read the serial port using CH340 in Read Multimeter USB Serial Port Module, but this serial port module could not be recognized later. Now use the ESP32 module used in the use of ESP32 to construct a ZIGBEE network transmission transfer and convert it to an RS232 serial port in a WiFi, so that you can get rid of the dependence on the computer UART and directly use the WiFi in the laboratory to complete the multimeter network. access to obtain multimeter measurement information.

2. Making the transfer board

1. ESP32 adapter module

The ESP32 MicroPython module uses the ESP32 module adapter board to build the interface circuit with the MAX3232 on the breadboard.

▲ Figure 1.2.1 MicroPython test module based on ESP32

▲ 图1.2.1 基于ESP32的MicroPython测试模块

(1) ESP32 module

Later, I found an ESP32 timing system for debugging, and the following is based on this module to complete the module transformation.

▲ Figure 1.2.2 ESP32 timing system

▲ 图1.2.2 ESP32计时系统

It is more convenient to use the UART1 to go out and lead out the interface.

▲ Figure A1.2.3 Modify ESP32 output interface

▲ 图A1.2.3 改造ESP32输出接口

(2) Outgoing interface

Ⅱ. Outgoing interface definition

Table 1-1 ESP32 output pin definitions

PIN1	PIN2	PIN3	PIN4
3.3V	GND	RXD	TXD

Ⅲ. Soldering output pins

According to the schematic diagram of the ESP32 timing system, the interface of UART1 is drawn as follows.

▲ Figure 1.2.4 Welding leads to UART1 interface

▲ 图1.2.4 焊接引出UART1接口

The corresponding pins of the UART of ESP32 are:

▲ Figure 1.2.5 ESP32 UART default pins

▲ 图1.2.5 ESP32 UART 缺省管脚

After testing, there is no output on PIN9 and PIN10 using UART1 directly. Now the modified mode is to use UART2 to complete the input and output settings on GPIO12 (RX) and GPIO14 (TX).

(3) ESP32 flash firmware

Flash the ESP32 firmware with Thonny. For specific methods, please refer to the Debugging Instructions of the ESP-12F Module Adapter Board Beta Version and download the MicroPython program. ESP8266-12F .

2. Test the ESP32 module

Test the UART1 function of the ESP32. After testing, verify that the UART is functioning properly.

from machine                import Pin,UART
import time
import machine

machine.freq(240000000)
uart1 = UART(2, baudrate=115200, rx=12, tx=14, timeout=10)

bz1 = Pin(21, Pin.OUT)
bz1.on()
time.sleep_ms(50)
bz1.off()
print("Test LED")

while True:
    uart1.write('hello')
    b = uart1.read(5)
    print(b)

    time.sleep_ms(250)

3. MAX3232 adapter module

Since the MAX3232 modules used are surface-mount modules, a one -minute pattern-making method is used to build a small board with a 100mil test pin interface, which is convenient to connect with the front ESP32 test board on the breadboard.

(1) Adapter board design

Design the adapter board, the schematic diagram and the PCB design diagram for rapid plate making are given below.

AD\Test\2022\MAX3232SIP.SchDoc

▲ Figure 1.2.3 Adapter board designed by Altium Design

▲ 图1.2.3 Altium Design设计的转接板

(2) Adapter board debugging

The function of the level transfer board is tested below. Send and receive the "hello" string using the UART of the ESP32 above. Measure the level of the output signal and short-circuit the RX and TX pins of the UART. Can get sent and received strings.

▲ Figure 1.2.7 Test RS3232 function after welding

▲ 图1.2.7 焊接后测试RS3232功能

▲ Figure 1.2.8 Test the output RS232 signal of the adapter board

▲ 图1.2.8 测试转接板的输出RS232信号

3. Connect the multimeter network

1. Read data

According to the original multimeter reading program: ShowPannelResult() , obtain the multimeter network reading protocol. The following program shows that the cycle of reading the multimeter is 25ms.

//---------------------------------------------------------------------------
void __fastcall TMainForm::Timer1Timer(TObject *Sender) {
    
    
    static int nShowResultCount = 0;
    if((nShowResultCount ++) >= 25) {
    
    
        nShowResultCount = 0;
        if(m_nShowResultFlag) {
    
    
            ShowPannelResult();
        }
    }
}

Read data and parse data program fragments.

int GetMeterValueAll(double * lfResult) {
    
    
    unsigned char ucBuffer[1024];
    ClearPort(PORT1);
    SendChar(0x55, PORT1);

    unsigned char ucChar;
    if(ReceCharL(&ucChar, PORT1, 20)) return 0;
    if(ucChar != 0x55) return 0;
    unsigned char ucMask;
    if(ReceCharL(&ucMask, PORT1, 20)) return 0;
    int nLength = ucMask;

    int i;
    for(i = 0; i < nLength; i ++) {
    
    
        if(ReceChar(&ucChar, PORT1)) return 0;
        ucBuffer[i] = ucChar;
        ucMask += ucChar;
    }

    if(ReceChar(&ucChar, PORT1)) return 0;
    if(ucChar != (ucMask ^ 0xff)) return 0;
    if(ReceChar(&ucChar, PORT1)) return 0;
    if(ucChar != 0xaa) return 0;

    float * p;
    int nNumber = nLength / 4;
    for(i = 0; i < nNumber; i ++) {
    
    
        p = (float *)&ucBuffer[i * 4];
        *(lfResult + i) = *(p);
    }

    return nNumber;
}

2. Definition of connection interface

Define the RS232 interface definition for networking with the multimeter. Define this interface the same as the PC UART definition. That is, the pins of DB9 are defined as:

PIN2：RXD
PIN3：TXD
PIN5：GND

▲ Figure 1.3.1 Interface Definition

▲ 图1.3.1 接口定义

3. Test and read the multimeter network

Use the following program to receive the following data after sending 0x55 characters.

from machine                import Pin,UART
import time
import machine

machine.freq(240000000)
uart1 = UART(2, baudrate=115200, rx=12, tx=14, timeout=100)

bz1 = Pin(21, Pin.OUT)
bz1.on()
time.sleep_ms(50)
bz1.off()
print("Test LED")

while True:
    _ = uart1.write(bytes([0x55]))
    b = uart1.read(50)
    print(b)

    time.sleep_ms(10)

Below is the information received from the multimeter.

b'U\x10\x83\xa8{7\xd6\xe5\x9484\x807\xba\x00\x00\x00\x00\xe6\xaa'
b'U\x10\x83\xa8{7\xd6\xe5\x9484\x807\xba\x00\x00\x00\x00\xe6\xaa'
b'U\x10\x8b\xe1j7\x93\x17\x9984\x807\xba\x00\x00\x00\x00\xc2\xaa'
b'U\x10:\x9b\x8e7\x93\x17\x9984\x807\xba\x00\x00\x00\x005\xaa'
b'U\x10:\x9b\x8e7\x93\x17\x9984\x807\xba\x00\x00\x00\x005\xaa'
b'U\x10\x83\xa8{70b\x9f84\x807\xba\x00\x00\x00\x00\x04\xaa'
b'U\x10:\x9b\x8e70b\x9f84\x807\xba\x17\xb7\xd1\xb8\xf0\xaa'
b'U\x10:\x9b\x8e70b\x9f84\x807\xba\x17\xb7\xd1\xb8\xf0\xaa'
b'U\x100b\x9f7\x93\x17\x998RI\x1d\xba\x00\x00\x00\x00\x9a\xaa'
b'U\x100b\x9f7\x93\x17\x998RI\x1d\xba\x00\x00\x00\x00\x9a\xaa'
b'U\x10:\x9b\x8e7r0\x9b8RI\x1d\xba\x00\x00\x00\x00n\xaa'

Fourth, UDP connection and transmission

1. Forward Python program

Below is the final ESP32 MicroPython program.

from machine                import Pin,UART
import time
import machine
import usocket,network

machine.freq(240000000)
uart1 = UART(2, baudrate=115200, rx=16, tx=17, timeout=50)

bz1 = Pin(21, Pin.OUT)
bz1.on()
time.sleep_ms(50)
bz1.off()
wlan = network.WLAN(network.STA_IF)
wlan.active(False)

wlan.active(True)
time.sleep_ms(100)
wlan.connect('TENDA626A', 'gniqouhz')

bz1.on()

while not wlan.isconnected():
    time.sleep_ms(100)

wlan.ifconfig()
bz1.off()

us = usocket.socket(usocket.AF_INET, usocket.SOCK_DGRAM)
sockaddr = usocket.getaddrinfo('0.0.0.0', 7654)[0][-1]
us.bind(sockaddr)

count = 0

while True:
    data,addr = us.recvfrom(1024)

    if len(data) > 0:
        _ = uart1.write(bytes([0x55]))

        count += 1
        if count >= 10:
            count = 0
            bz1.on()
            time.sleep_ms(5)
            bz1.off()

        b = uart1.read(50)

        if type(b) == bytes:            
            if len(b) > 0:
                us.sendto(b, addr)

2. Modify the MEGA program

PC software:

D:\zhuoqing\window\cb\MyResearch\Test\TestAD5344\M8BL_BAS\M8BL_BAS.exe

The modified program can complete the original program function based on UART.
▲ Figure 1.4.1 Procedure after testing

▲ 图1.4.1 测试后的程序

※ Summary ※

This article gives the process of forming a multimeter networking conversion module in ESP32. After the transformation, the universal networking data can be accessed through UDP.

■ Links to related literature:

● Links to related charts:

Figure 1.2.1 MicroPython test module based on ESP32
Figure 1.2.2 ESP32 timing system
Figure A1.2.3 Modify ESP32 output interface
Figure 1.2.4 Soldering the UART1 interface
Figure 1.2.5 ESP32 UART default pins
Figure 1.2.3 Adapter board designed by Altium Design
Figure 1.2.7 Test RS3232 function after soldering
Figure 1.2.8 Test the output RS232 signal of the adapter board
Figure 1.3.1 Interface Definition
Figure 1.4.1 Procedure after testing

Using the ESP32 module to make a multimeter networking adapter module